An approach to reduce pilot contamination in large-scale MIMO systems

A large-scale MIMO multi-cell system is considered where the desired cell bears pilot contamination. Multiple neighbor cells and the desired cell use the same pilot position to transmit training symbols, and training symbols from neighbor cells have a large received power. The channel estimation of the desired cell will be significantly deteriorated. In order to reduce the impact of pilot contamination on uplink channel estimate and bit error rate performance, a pilot pattern design is proposed where zero pilot symbols are inserted into the pilot sequence. The first neighbor cell uses the same training sequence as the desired cell but utilizes different pilot positions, and the remaining neighbor cells use orthogonal training sequences different from the desired cell and the first neighbor cell. In the studied MIMO OFDM transmission scheme, the base station of desired cell uses LS scheme for uplink channel estimation. The computer simulation results show that the approach can both significantly reduce pilot contamination and be easy to pilot multiplexing.